# year    value 
 1980 8.148337 
 1981 8.319131 
 1982 8.141983 
 1983 7.770472 
 1984 8.137972 
 1985  8.11393 
 1986 8.305487 
 1987 8.284126 
 1988 8.369722 
 1989 8.489266 
 1990 8.316776 
 1991 8.145317 
 1992 7.995002 
 1993 8.072693 
 1994  8.45936 
 1995 8.503952 
 1996 8.722973 
 1997 8.705194 
 1998 8.848948 
 1999  8.68572 
 2000 8.997447 
 2001 9.213466 
 2002 8.813476 
 2003 9.102179 
 2004 9.003735 
 2005 9.063862